Commit 
0dbaee3b37e118a (net: Abstract default ADVMSS behind an
accessor.) introduced a possible crash in tcp_connect_init(), when
dst->default_advmss() is called from dst_metric_advmss()
Reported-by: George Spelvin <linux@horizon.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 
        .destroy                =       ipv4_dst_destroy,
        .check                  =       ipv4_blackhole_dst_check,
        .default_mtu            =       ipv4_blackhole_default_mtu,
+       .default_advmss         =       ipv4_default_advmss,
        .update_pmtu            =       ipv4_rt_blackhole_update_pmtu,
 };
 
 
        .destroy                =       ip6_dst_destroy,
        .check                  =       ip6_dst_check,
        .default_mtu            =       ip6_blackhole_default_mtu,
+       .default_advmss         =       ip6_default_advmss,
        .update_pmtu            =       ip6_rt_blackhole_update_pmtu,
 };